Embodiments of the present invention are directed devices which induce movement in cantilevered arms. Such devices measure changes in resonance of such arms upon changes in mass. These changes in resonance are used to determine mass related parameters. As used herein, the term “mass related parameters” refers to values which can be measured or calculated from such changes in resonance in cantilevered arms induced or caused by a change in the mass carried by such arm.
Embodiments of the present invention have particular applications in measuring fluids contained or flowing in microfluidic devices. As used herein, the term “microfluidic” refers to devices which contain approximately 10 micro-liters or less.
As used herein, the term “analyte” refers to a compound or composition which is of interest. By way of example, without limitation, such analyte can be a compound for which information as to its presence or absence is desired, or its concentration, or the mass of the compound in the solution in which it is dissolved.
As used herein, the term “solute” refers to a compound that is dissolved. The compound or mixture of compounds in which the solute is dissolved is the solvent.
Chromatography is a technique in which compounds held in solution are separated from each other by the different affinity such compounds exhibit to a media held stationary or moving in a different manner than the solution in which the compounds are held. High performance liquid chromatography (HPLC) uses pressure to compel solutions carrying compounds of interest through an immobilized media of packed particles or functional equivalent or a monolith plug of porous material. The immobilized media is often referred to as the stationary phase. A compound which exhibits affinity for a stationary phase will leave the stationary phase, and elute, as a concentration of the compound in the solution. Detectors of the compound measure the concentration as a peak. Chromatographic systems are known in the art and generally comprise a pump, sample injector and detectors. Such systems are available from several vendors.
Presently, there is a need for devices and methods that will provide a analytical value relating to mass of a compound that can be used with separations techniques such as chromatography.